1. Field of the Invention
The invention relates generally to the conversion of solid biomass to bio-oil, and more particularly to the conversion of lingo-cellulosic biomass.
2. Description of the Related Art
Processes have been proposed for the conversion of bio-mass to liquid products, generally referred to as bio-oil. Bio-oils are notorious for having a poor stability, due to their high oxygen content. In addition, bio-oils tend to be characterized by a low pH and a high Total Acid Number (“TAN”).
It has been proposed to reduce the oxygen content of bio-oils by subjecting them to (catalytic) hydrotreatment. Because of the consumption of expensive hydrogen associated with hydrotreatment processes, such processes are too expensive to be economically viable. Moreover, part of the bio-oil is converted to coke during the hydrotreatment process, due also to the inherent instability of the bio-oil.
To reduce the coke formation during hydrotreatment it has been proposed to subject the bio-oil to a hydrogen treatment at relatively mild temperatures. Although this measure reportedly reduces the loss of bio-oil to coke formation, it also further increases the consumption of hydrogen.
Thus, there is a particular need for a biomass conversion process in which a bio-oil is produced having a reduced oxygen content. There is also a need for such a process in which the use of expensive reactants, such as hydrogen, is minimized or avoided entirely.